The invention relates to an intake manifold of the type having an electrically conductive wall about a flow channel which can be heated at least in part by the wall.
Such an intake manifold is known. It consists of a cast aluminum alloy and has the function of supplying the mixture of gasoline droplets and air prepared in the carburetor or by the single-point injection system to the individual cylinders of the internal combustion engine. During a cold start, however, the mixture tends to condense on the internal surface of the intake manifold, which in the final analysis causes the mixture to become leaner and can result in a poor operating behavior of the engine. It is therefore necessary to make a richer mixture available for this phase of the operation. However, this causes a high fuel consumption and high emission values.
To avoid this disadvantage, provisions have been made for the version addressed at the beginning to construct the intake manifold at least in part with a double wall and to pass a coolant through the space between the two walls in order to bring about rapid heating. In the cold-starting phase, however, the coolant has not yet been heated sufficiently to eliminate the problem addressed effectively.
Further problems may arise with the version named at the beginning when the hot engine, which has just been switched off, is started once again. In a corresponding operating situation, a great accumulation of heat may be observed in the area of the cylinder head, which results in strong heating of the carburetor over the aluminum intake manifold. The fuel in the carburetor is evaporated by this heating and it becomes difficult to start the engine once again. The proposal has therefore already been made to provide a flange, which may consist, for example, of rubber and acts as a thermal insulator, between the carburetor and the intake manifold. The procurement and installation of such a flange, however, require additional expenditure.
According to a different proposal, the provision of an electrical heater for heating the combustion mixture in the intake manifold, which consists of a metallic material, is already known. However, the initially addressed problem with respect to the cold starting as well as with respect to the hot starting cannot be eliminated in a satisfactory manner with this heater.